Substituent Effect on the Electronic Structure of Sulfines: Molecular Orbital Treatment

The electronic structure and ground state properties of the gaseous sulfine H₂CSO and some of its derivatives were studied at the RHF, MP2, and B3LYP levels. The calculations showed that the Z-isomer is more stable than the E-one and their difference in energy depends on their level of calculation, basis set, and substituent. The factors affecting the isomer stability are the electrostatic interactions, the steric factor, and π-electrons delocalization. The substituent has little effect on the geometry of the CSO moiety but greatly affects its charge distribution and polarizability. The ΔE value of the E- to Z-isomerization process via rotation of the S═O bond was calculated. The substituent has an appreciable effect on both the geometry and energy barrier of isomerization depending on its electronegativity, electrostatic attraction, and effect on π-delocalization over the molecule.

Keywords:

• Electrostatic interaction
• MO calculations
• substitution
• sulfine
• Z- to Eisomerization

Notes

^a Results taken from ref. [38] and references there in.

^b Our results.

^c Microwave spectrum results, Ref. [28].

^a Values calculated at the RHF level.

^b Values calculated at the MP2 level.

^c Values calculated at the B3LYP level.

^d Values in italics refer to experimental results.

^a Values calculated at the RHF level.

^b Values calculated at the MP2 level.

^c Values calculated at the B3LYP level.

^d Values in italics refer to experimental results.

^a Values in parentheses correspond to zero-point energy (kcal/mol) and thermal correction (TC) between two brackets (kcal/mol).

^b E _a = ΔE* + Δ(ZPE) + Δ(TC) + RT.

^c ΔH = ΔE + Δ(ZPE) + Δ(TC).